Left Posterior Fascicular Block is very rare intraventricular defect! The condition can cause a heart rhythm disorder and right axis deviation can be clinical sign for the rhythm disorder.
With all EKG recordings requires a differential diagnosis and EKG is not very reliable analysis without confirmation of possible disorders. Doctor must first exclude (on clinical grounds) other causes of right axis deviation such as cor pulmonale. An echo can rule out cor pulmonale and that disorder leads to an increase in bulk of the right ventricle of the heart, generally caused by chronic diseases or malfunction of the lungs. This condition can lead to heart failure. Also, to rule out is pulmonary right-heart disease, pulmonary hypertension, etc., because these conditions can result in the identical ECG picture!
Its highly unlikey you will have a heart attack. Advanced condition could lead to heart failure and that is a decrease of the heart's pumping ability, and you would have symptoms of shortness of breath, fatigue, possibly chest pain, etc. before any serious consequences...its a progressive disorder and can be treated if there is a medical problem.
Apparently RAD is very common in tall people.